The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems such as semiconductor processing systems may be used to deposit film layers, metal layers or other types of layers onto a substrate such as a semiconductor wafer. The substrate processing system may include one or more processing station assemblies. In a substrate processing system, substrate handling can have a significant impact on cost and throughput. To increase throughput and reduce cost, the substrates need to be processed through different processing steps in the most efficient manner and with minimal or no contamination.
In some substrate processing systems, the substrates are moved from a substrate cassette to a reactor and then back to a substrate cassette or another location. To improve throughput and reduce substrate handling, a single reactor may include multiple, sequential processing station assemblies. In this type of substrate processing system, the substrate is moved to the reactor, processed sequentially in the processing station assemblies and then moved to a substrate cassette or another location. This processing arrangement tends to increase throughput by reducing substrate handling.
Referring now to FIG. 1, an example of a substrate processing system 8 includes a multi-station, sequential processing (MSSP) reactor 10 with multiple stations 14-1, 14-2, 14-3 and 14-4 (collectively stations 14) and pedestals 16-1, 16-2, 16-3 and 16-4 (collectively pedestals 16). While four stations are shown, additional or fewer stations can be used. A vacuum transfer chamber 18 is in communication with the reactor 10 via valves (not shown) and includes a substrate handling robot 22. A load lock 24 is in communication with the vacuum transfer chamber 18 via valves (not shown).
A substrate handler 26 includes a substrate handling robot 28 and substrate cassettes 30. The substrate handling robot 28 loads a substrate from one of the substrate cassettes 30 into the load lock 24 for cleaning. When the load lock 24 is ready, the substrate handling robot 22 transfers the substrate to one of the stations 14 of the reactor 10.
Referring now to FIG. 2, an example of an indexing mechanism 54, which is a two-axis wafer transfer mechanism, is shown. The mechanism includes a transfer plate 55, a spindle assembly 56 and a multiple carrier rings 16-1, 16-2, 16-3, and 16-4. As can be appreciated, the indexing mechanism 54 takes up a significant amount of chamber volume of the reactor. The indexing mechanism 54 is always present in the reactor because it cannot retract or otherwise be removed from the chamber volume. The indexing mechanism 54 also requires anomalous features in the design of a pedestal 58 to enable transfer onto the indexing mechanism 54. Moreover, substrate displacement tends to occur during substrate transfer via the indexing mechanism 54. The substrate displacement can cause cumulative and increasing eccentricity in substrate placement on subsequent pedestals.